• 한국결정성장학회지
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• 제8권3호
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• pp.493-497
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• 1998

부활제인 $Eu_2O_3$의 농도를 변화시킨 $Sr_{1-x}Eu_xAl_2O_4$(x=0.005~0.2mol%)계 장잔광 형광체를 98%Ar+2% H2의 환원분위기에서 고상반응시켜 합성한 후 X-선 회절실험과 장잔광 축광재료로서 가장 중요한 발광특성과 장잔광 특성을 조사하였다. $SrAl_2O_4:Eu^{2+}$계 형광체는 $Eu_2O_3$의 농도에 관계없이 녹황색의 520nm파장을 최대 발광파장으로 하는 발광스펙트럼을 나타내었으나, 발광특성을 크게 저해하지 않는 SrAl2O4의 단일상을 얻기 위한 농도는 0.05mol% 이하가 적절하였다. 또한 $SrAl_2O_4:Eu^{2+}$ 형광체의 잔광강도는 $Eu_2O_3$의 농도에 무관하게 시간에 따라 모든 시료에서 지수 함수적으로 감소하나, Eu2O3의 농도가 0.05mol% 이하인 경우에 발광의 감쇠속도가 작은 뛰어난 장잔광특성을 나타내었다.

• 한국수소및신에너지학회논문집
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• 제19권6호
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• pp.505-513
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• 2008

The two-step thermochemical cycle was examined on the $CeO_2$, YSZ, and $ZrO_2$-supported $NiFe_2O_4$ to investigate the effects of support material addition. The supported $NiFe_2O_4$ was prepared by the aerial oxidation method. Thermal reduction was conducted at 1573K and 1523K while water-splitting was carried out at 1073K. Supporting $NiFe_2O_4$ on $CeO_2$, YSZ and $ZrO_2$ alleviated the high-temperature sintering of iron-oxide. As a result, the supported $NiFe_2O_4$ exhibited greater reactivity and repeatability in the water-splitting cycle as compared to the unsupported $NiFe_2O_4$. Especially, $ZrO_2$-supported $NiFe_2O_4$ showed better sintering inhibition effect than other supporting materials, but hydrogen production amount was decreased as cycle repeated. In case of $CeO_2$-supported $NiFe_2O_4$, improvement of hydrogen production was found when the thermal reduction was conducted at 1573K. It was deduced that redox reaction of $CeO_2$ activated above 1573K.

• 전기학회논문지
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• 제67권4호
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• pp.543-548
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• 2018

Ferroelectric $Bi_4Ti_3O_{12}$ films were deposited on $SrTiO_3(100)$ and Si(100) substrate by using conductive $SrRuO_3$ films as underlayer, and their ferroelectric and electrical properties were investigated depending on crystal structure and orientation. C-axis oriented $Bi_4Ti_3O_{12}$ films were grown on well lattice-matched pseudo-cubic $SrRuO_3$ films deposited on $SrTiO_3(100)$ substrate, while random-oriented polycrystalline $Bi_4Ti_3O_{12}$ films were grown on $SrRuO_3$ films deposited on Si(100) substrate. The random-oriented polycrystalline film showed a good ferroelectric hysteresis property with remanent polarization ($P_r$) of $9.4{\mu}C/cm^2$ and coercive field ($E_c$) of 84.9 kV/cm, while the c-axis oriented film showed $P_r=0.64{\mu}C/cm^2$ and $E_c=47kV/cm$ in polarizaion vs electric field curve. The c-axis oriented $Bi_4Ti_3O_{12}$ film showed a dielectric constant of about 150 and lower thickness dependence in dielectric constant compared to the random-oriented film. Furthermore, the c-axis oriented $Bi_4Ti_3O_{12}$ film showed leakage current lower than that of the polycrystalline film. The difference of ferroelectric properties in two films was explained from the viewpoint of depolarization effect due to orientation of spontaneous polarization and layered crystal structure of bismuth-base ferroelectric oxide.

• 센서학회지
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• 제30권4호
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• pp.191-195
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• 2021

Pure ZnFe₂O₄ and Fe₂O₃-ZnFe₂O₄ hetero-composite spheres were prepared by ultrasonic spray pyrolysis of a solution containing Zn- and Fe-nitrates. Additionally, the sensing characteristics of these spheres in the presence of 5 ppm ethanol, benzene, p-xylene, toluene, and CO (within the temperature range of 275-350 ℃) were investigated. The Fe₂O₃-ZnFe₂O₄ hetero-composite sensor with a cation ratio of [Zn]:[Fe]=1:3 exhibited a high response (resistance ratio = 140.2) and selectivity (response to p-xylene/response to ethanol = 3.4) to 5 ppm p-xylene at 300 ℃, whereas the pure ZnFe₂O₄ sensor showed a comparatively lower gas response and selectivity. The reasons for the superior response and selectivity to p-xylene in Fe₂O₃-ZnFe₂O₄ hetero-composite sensor were discussed in relation to the electronic sensitization due to charge transfer at Fe₂O₃-ZnFe₂O₄ interface and Fe₂O₃-induced catalytic promotion of gas sensing reaction. The sensor can be used to monitor harmful volatile organic compounds and indoor air pollutants.

• 한국재료학회지
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• 제14권11호
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• pp.813-820
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• 2004

The electrolytic reduction of spent oxide fuel involves the liberation of oxygen in a molten LiCl electrolyte, which is a chemically aggressive environment that is very corrosive for typical structural materials. So, it is essential to choose the optimum material for the process equipment handling molten salt. In this study, corrosion behavior of Haynes 263, 75, and Inconel X-750, 718 in molten salt of $LiCl-Li_{2}O$ under oxidation atmosphere was investigated at $650^{\circ}C\;for\;72\sim360$ hours. At $3\;wt\%\;of\;Li_{2}O$, Haynes 263 alloy showed the highest corrosion resistance among the examined alloys, and up to $8\;wt\%\;of\;Li_{2}O$, Haynes 75 exhibited the highest corrosion resistance. Corrosion products were formed $Li(Ni,Co)O_2,\;LiNiO_2\;and\;LiTiO_2\;and\;Cr_{2}O_3$ on Haynes 263, $Cr_{2}O_3,\;NiFe_{2}O_4,\;LiNiO_2,\;Li_{2}NiFe_{2}O_4,\;Li_{2}Ni_{8}O_10$ and Ni on Haynes 75, $Cr_{2}O_3,\;(Al,Nb,Ti)O_2,\;NiFe_{2}O_4,\;and\;Li_{2}NiFe_{2}O_4$ on Inconel X-750 and $Cr_{2}O_3,\;NiFe_{2}O_4\;and\;CrNbO_4$ on Inconel 718, respectively. Haynes 263 showed local corrosion behavior and Haynes 75, Inconel X-750, 718 showed uniform corrosion behavior.

• 한국세라믹학회지
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• 제36권12호
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• pp.1327-1334
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• 1999

Behaviors of abnormal expansion during calcination process of Ba2Ti9O20 ceramics and its related effects on the sintering characteristics were investigated as a function of precursors. When BaCO3 and TiO2 powders were used as starting materials. BaTi4O9 phase which has relatively large molar volume was formed drastically with abnormal ex-pansion during the calcination at 95$0^{\circ}C$ to 115$0^{\circ}C$ ON the contrary using BaTiO3 and TiO2 powders as starting materials led to retardation of the formation of BaTi4O9 phase and concurrently suppressed the abnormal expansion during cal-cination process. Especially the calcined powder of BaTiO3 and TiO2 had advantages in the densification and formation of Ba2Ti9O20 single phase in the sintering process.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2018년도 춘계학술발표대회
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• pp.198-201
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• 2018

사이버 공간과 물리적 공간의 서비스를 접목하는 O2O(Online to Offline) 비즈니스 모델은 산업과 일상 생활에서 다양한 서비스들을 제공하고 있다. 이러한 세계적인 트랜드인 O2O 서비스의 국내 외 동향을 살펴보고 4가지 유형별로 서비스의 특성을 살펴보고 분류하였다. 또한, 일반적인 세계 시장과는 흐름과 다소 다른 양상을 띠고 있는 국내 O2O 서비스 시장에서 활성화 되고 있는 신 비즈니스 모델인 O4O(Online for Outline)를 소개하며, O4O 서비스의 기술적인 전략인 디지털 트윈(Digital Twin)의 접목을 제안한다.

• 한국전기전자재료학회논문지
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• 제18권1호
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• pp.57-61
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• 2005

The microwave dielectric properties of 0.6TiTe$_3$O$_{8}$-0.4MgTiO$_3$ ceramics with H$_3$BO$_3$-SnO were investigated to improve the sintering condition for the LTCC. According to the X-ray diffraction patterns, 0.6TiTe$_3$O$_{8}$-0.4MgTiO$_3$ ceramics with H$_3$BO$_3$-SnO had the columbite structure of TiTe$_3$O$_{8}$ phase and the ilmenite structure of MgTiO$_3$ phase and there were no second phase. Increasing the addition of H$_3$BO$_3$-SnO, the density and dielectric constant of the 0.6TiTe$_3$O$_{8}$-0.4MgTiO$_3$ ceramics were increased but the quality factor was decreased. The temperature coefficient of resonant frequency was shifted to the negative(-) direction with addition of H$_3$BO$_3$-SnO.EX>-SnO.

• 한국세라믹학회지
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• 제23권3호
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• pp.53-61
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• 1986

A gas sensor which has been made by wet process had fabricated by coating each of the mixture on alumina tube and firing at 85$0^{\circ}C$ for 3hrs. A gas concentration such $H_2$, CO, $C_3H_8$, $C_2H_2$ and $CH_4$ vs its detection voltage characteristics has been in-vestigated on $SnO_2-In_2O_3-MgO$ system doped with PdO, $La_2O_3$, $ThO_2$, NiO and $Nb_2O_5$ The optimum sensitivity composition for various gases were 90w/o $SnO_2$-9w/o $In_2O_3$-1w/o MgO for $H_2$, $C_2H_2$ CO and $C_3H_8$ and 95w/o $SnO_2$-4w/o $In_2O_3$-1w/o MgO for $CH_4$. The sample which has been made by wet process than dry process had predominated sensitivity for each gases and particle size of the sample coprecipitated with PH=9 was 0.1${\mu}{\textrm}{m}$ The $SnO_2$-In2_O_3-MgO$ system doped with 2w/o $Nb_2O_5$ and NiO was the most sensitive for $H_2$ and $C_2H_2$ gas. In $SnO_2$-In2_O_3-MgO$ system doped with $ThO_2$ the sensitivity of $H_2$ gas was decreased but CO gas was in-creased when dopant con was increased.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.464-467
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• 2002

$TiO_{2}-Co_{3}O_{4}$ humidity sensors were fabricated by conventional ceramic process and their humid sensing characteristics were investigated. The sample which was added 10wt% $Co_{3}O_{4}$ and heat-treated $1200^{\circ}C$ showed the highest sensitivity to humidity changes and improved a linearity. As $Co_{3}O_{4}$ content was increasing, the sensor consists a uniform pore distribution and grain in the surface. This was analyzed by SEM photographs.